1. Technical Field
This technology relates to digital camera systems primarily for capturing still images and camera systems such as video cameras primarily for capturing moving images. In particular, it relates to camera systems having an optical system that is capable of varied proportion zooming. It also relates to camera bodies, interchangeable lens units, focus control methods, and programs, for use in camera systems.
2. Description of the Related Art
JP H04-42108A discloses a camera with an inner focus-type zoom lens. Inner focus-type zoom lenses change the focus state when the focal distance is altered through varied proportion zooming. JP H04-42108A discloses performing contrast-type auto focusing in order to keep the optical image of the object being captured in focus during varied proportion zooming. JP H04-42108A discusses the difficulty of focusing accurately during varied proportion zooming using contrast-based auto focusing. It also discloses determining the distance to the object being captured, and then, based on the results of this determination, selecting one of a plurality of focus lens group movement locuses that are stored in a memory portion, and moving the focus lens group based on that movement locus.
JP H04-42108A thus discloses improving the accuracy of camera system focusing during varied proportion zooming. However, with the camera system that is disclosed in JP H04-42108A, the focus lens group is moved based on a movement locus, and thus a good focus state cannot be maintained in a case where there is movement, for example, in the object that is to be kept in good focus during variable proportion zooming. Further, depending on the limitations of the means for driving the focus lens group, contrast-based auto focusing may not be possible when variable proportion zooming is conducted quickly. It may not be possible to maintain a good focus state in this case. In other words, JP H04-42108A does not disclose the maintaining of a good focus state regardless of the speed of zooming during variable proportion zooming.
It is an object of the present technology to provide a camera system, a camera body, an interchangeable lens unit, a focus control method, and a program, with which a good focus state can be maintained regardless of the speed of zooming during variable proportion zooming.